Portable electric tool



March 2, 1937. k oRss 2,072,551

PORTABLE ELECTRIC TOOL Filed May 18, 1936 2 Sheets-Sheet l mvmox.fkITH/Of P .FORJ'S rd mn ATTORNEY.

March 1937. F. P. FORSS PORTABLE ELECTRIC TOOL Filed May 18, 1936 2Sheets-Sheet 2 INVENT OR. EilfH/Offi F0555 W My 6 ATTORNEY.

Patented Mar. 2, 1937 PATENT OFFICE PORTABLE ELECTRIC TOOL' Frithiof 1.Fans, Aurora, 111.. amignor to Independent Pneumatic Tool 00., Chicago,111., a corporation of Delaware Application May 18,

1: Claims.

This invention relates to portable electrically operated hand tools fordrilling, screw driving. grinding, and the like.

The tool to which my invention relates is relatively small in size andlight in weight and has a pistol grip handle at its rear end whereby theoperator may hold and operate the tool in one .hand: The spindle of thetool is at its front end and is provided with a chuck or other device,whereby a drill bit. screw driving attachment, grinding wheel, or otherdesired working element may be attached to the spindle for rotationthereby. The handle of the. tool may be made hollow to accommodate theelectric supply cable for the motor, and, if desired, provide an airduct for the intake of air for the cooling system for the motor.

The general purpose and object of my invention is to support the brushassembly and the supply cable for the motor entirely by the motor casinggo of the tool and not by the grip handle, thereby enabling the griphandle to be made in one piece and be removed in its entirety from themotor case without disturbing the brush assembly or the cableconnections with the motor. The advantage of this is that the brushholders, brushes and commutator of the motor may on removal of thehandle be inspected while the motor is running and the commutatorcleaned with a piece of sand paper as done with large stationary motors.

A further object of my invention is to support the supply cable from themotor case by providing the bearing cup at the rear end of the motorwith a depending bracket to which the cable may be conveniently clampedor secured. This construction also provides open spaces above and belowthe cup and on opposite sides of the bracket to give an unobstructedview of the commutator and the brush assembly on the removal of thhandle.

A further object of my invention is to provide a motor for the tool ofthe regular universal type with a distributed stator winding, therebyassuringhigh power and emciency with a stator of small diameter, andalso to provide a space between the stator and the motor casing for theswitch device and the manually operable parts therefor without addingsize to the tool.

A further object of my invention is to employ a cam and levercombination for operating the switch device. By the use of thiscombination the operating cam and lever can be placed in a position mostconvenient for the thumb of the operator's hand holding the tool forturning on and off the electrical current to the motor.

1936, Serial No. 30,311

The invention consists further in the features hereinafter described andclaimed.

Fig. l is a side view of the improved tool, the pistol grip handlemember being shown in full lines removed from' the tool;

Fig. 2 is an enlarged longitudinal, vertical sectional view of the toolwith the handle member in place at the rear end of the motor casing,parts being shown in elevation;

Fig. 2a shows the interlocking connection be- 10 tween the upper end ofthe handle member and the top part of the motor casing;

Fig. 2b shows the interlocking connection between the lower portion ofthe motor casing and the handle member;

Fig. 3 is a rear view of the tool with the handle removed and onapproximately the scale of Fig. 2;

Fig. 4 is a horizontal sectional view taken on line 4-4 of Fig. 3;

Fig. 5 is a similar sectional view taken on line 5-5 of Fig. 2, withparts in elevation. to show the cam and lever combination for operatingthe switch device for the motor;

Figs. 6 and 7 show the action of the cam means referred to; and

Fig. 8 is a sectional view taken on line 8-8 oi Fig. 2.

In the drawings, I indicates the outer casing of the tool enclosing theelectric motor which rotates the chuck shaft or spindle 2 at the frontend of the tool. The motor, as shown, is of the regular type having itsarmature 3 rotatable in and encircled by a stator 4. The motor assemblyis located in the lower portion of the casing I, providing a space 5above the motor for the switch device 6 and its combination cam andlever actuating mechanism to be later described.

The armature shaft I is Journaled at its ends in ball bearings 8, 9, onelocated at the front end of the motor case I and the other located atthe rear end of said case. The forward bearing 8 is supported in a plateIll which closes the front end of the-motor case I and forms the rearwall of a gear housing to be presently described. The rear bearing issupported in a cup I I located between and cast integral with'a pair oflugs l2, l2 extending rearwardly from the'side walls of the motor caseas shown in Fig. 3.

The cup I I is provided with a depending bracket I! cast integral withthe cup and comprised of a pair of arms I3a, I3b spaced axially of thetool and connected at their lower ends on one side by a curved yokepiece II. The latter accommodates the end of the cable ii at the tool,said cable containing electric supply wires I i, ll

for the motor of the tool. The cable is clamped in the yoke piece by aclamp plate or strip I8, which as shown in Figs. 2 and 3, spans the openside of the yoke piece and is secured to the arms by fastening screwsI9.

The commutator 20 of the motor is located within the motor casing Iadjacent its rear end and is engaged by a pair of carbon brushes 2I, 22.These brushes are also located wholly within the motor casing I, beingsupported therein by a ring-shaped plate 23 of suitable insulatingmaterial. The ring 23 surrounds or encircles the commutator 26 and isheld in place in the motor case I against a seat 24 by one or morefastening screws 25, as indicated in Figs 3 and 4. In the particularembodiment shown, the ring23 is located adjacent the inner end of thecommutator, the brushes being disposed on the outer side of the ring andslidably mounted in brush holders 26, 21, one for each brush.

Each brush holder 26, 21 is preferably in the form of a metal strip,shaped to provide a channel section 28 intermediate its ends to receivea brush and anchored at its ends to the ring 23 by fastening elements29, 30 which may be of the screw type as shown. The element 29 providesan anchor for one end of a spiral spring 3|, the other end of the springbearing against the outer end of the associated brush to press the brushagainst the commutator, as shown. The other element 30 at each brushholder provides a binding post for connecting the brushes in the motorcircuit.

The handle member 32 for the tool is releasably secured to the rear endof the motor casing I by a number of fastening screws 33, 34. The screw33 takes into a tapped lug 35 at the upper edge of the motor case, whilethe screw 34 screws into a tapped hole in the cable supporting bracket'I3, as shown in Fig. 2. The handle member provides a cover for the rearend of the motor casing and has recesses 36, 36 in its side walls toreceive the similarly shaped projections I2 on the motor-case.

The lug 35 at the top of the motor case interlocks with a recess 31 inthe top portion of the handle member, while a lug 38 on the handlemember interlocks with a recess 39 in the lower edge of the motor case,as shown in Figs. 2a and 2b, respectively. The lugs and projectionsreferred to interlock the handle with the motor case and also serve asmeans for centering the parts when assembling them, I

The lower portion 40 of the handle member 32 extends below the motorcase I in substantially normal relation thereto and is made tubular inshape, as shown in Fig. 2b, to provide a pistol grip for the fingers ofthe hand of the operator holding and operating the tool. The portion 46is made hollow to accommodate the cable I5 and the supporting bracketI3, when the parts are assembled. The lower end of the portion 46 may beclosed by a fiber plate 4| set in a recess in the edge of the handle asshown. This plate centers the cable with respect to the handle and maybe provided with one or more air intake openings 42 in addition to thecentral opening 43 for the cable.

The motor is equipped at its forward end with a rotary fan having a disc44 fixed to the armature shaft 1 between the armature 3 and the plateI0. The disc 44 is provided with fan blades 45 which in the rotation ofthe motor draws air through the motor from its rear end and dischargessuch air out of the case through a number of vent openings 46. Thelatter are provided in the motor casing I adjacent the periphery of thefan and may be disposed in tangential relation to the fan as disclosedin my patent No. 1,652,401, granted December 13, 1927.

Air intake openings 41 may also be provided in the motor case I inadvance of the brush plate 23 as shown in Fig. l.

The spindle 2 is arranged on the side of the armature shaft 1 oppositethe grip portion 40 of the handle member 32. Said spindle is driven fromthe shaft I by a reducing gear 48 in mesh with gear teeth 49 provided inthe forward end of the shaft 1. The gear 48 is fixed to the spindle 2and is located in the gear housing, the front cover plate 50 of which issecured to the forward end of the motor casing I by a number of screws5| as shown. The spindle 2 is journaled in ball bearings 52, 53, onecarried by the plate In and the other carried by the gear housing cover50. The spindle 2 in the particular tool shown is equipped with a chuck54 for holding a drill bit.

The switch device 6 is of the conventional snap type obtainable on themarket and is supported in the motor case I by a metal strip 55extending across the motor case in the space 5 beneath the switch blockor housing 56. The latter seats against the cover plate I6 in a socketformed by a U-shaped flange 51 provided on said plate. The strip 55 hasone or more upturned lugs 58, 58 to hold the switch in place, as shownin Fig. 8. The top wall of the motor case may be provided with recesses59, 59 to receive the upper corners of the switch block as shown in saidfigure. The ends of the strip 55 are engaged in apertures 60, 60 in themotor case as shown.

The actuator 6I of the switch 6 extends toward the rear of the tool andis engaged by the forked end 62 of a lever 63 fulcrumed intermediate itsends on a screw 64 depending from the top wall of the motor case asshown in Fig. 2. The rear end of the lever 63 is engaged by the innerend of a second lever 65 arranged at right angles to the main lever 63and fulcrumed in the motor case I on a pivot pin 66 between a pair oflugs or ears 61, 61a as shown in Fig. 5. The free or outer end of thesupplemental lever 65 extends out of the motor case through a. slot 68therein as shown in Figs. 6 and 7. This slot is located adjacent therear end of the motor case, thus positioning the outer end of thesupplemental lever 65 in a position to be readily engaged by the thumbof the hand of the operator holding and operating the tool. The tool isgrasped and held with the thumb of the hand on the side of the motorcase from which the lever 65 extends. I

The inner end of the lever 65 is provided with a cam slot 69 to move themain lever 63 to actuate the switch 6 as the outer end of thesupplemental lever 65 is moved to the opposite ends of the slot 68. Inthe particular embodiment shown, the switch is off when the outer end ofthe lever 65 is at the upper end of the slot 68, whereas the switch ison when the outer end of the lever 65 is at the lower end of said slot,as indicated in Figs. 7 and 6, respectively. The free end of the lever63 works in said cam slot, which by its angularity to the lever 63swings the latter back and forth in the up and down movement of thelever 65. One edge of the cam slot moves the lever 63 in one direction,while the other edge of the slot moves the lever in the oppositedirection. The upward movement of the lever 65 is limited by its innerend striking the top wall 01' the motor case. The downward movement ofthe lever 65 is stopped by the closed end of the cam slot 69 strikingthe engaged end of the main lever 63. The lever 63 enables the switchdevice 6 to be seated against the plate III at the front end of themotor, yet be operated from adjacent the rear end of said case by thethumb of the operator's hand holding and using the tool.

The handle member 32 is in one piece, being die cast. The motor case I,bearing cup ii and cable bracket i3 are also in one piece being diecast, as are the other casing parts of the tool. Light metal is used toprovide a tool which is relatively light in weight. The motor and otherparts are so proportioned as to provide a tool smaller in size andlighter in weight than ordinary tools with equal power. The advantagesof such construction are that the tool can be held in and operated byone hand and be usable in close or confined quarters.

With the support for the brush assembly and the supply cable i5 confinedto the motor case I, the handle member 32 is relieved of this duty,

and thus may be removed in its entirety from the tool without disturbingthe brush assembly or the connection of the supply cable to thetool.

This permits running of the motor for inspection of the brush assemblyand the commutator while the handle is removed from the tool asindicated in Figs. 1 and 3. Also an unobstructed view of the brushassembly and the commutator is provided on removing the handle member asthe entire rear portion of the motor case is opened on taking oil. thehandle member. The upper brush and the commutator is accessible in thelarge open space above the bearing cup ll, while the lower brush isaccessible below the cup through the open spaces on opposite sides ofthe cable bracket i 3, as clearly shown in Fig. 3. The space 5 above themotor enables the upper brush 2i to be replaced when worn, said brushbeing placed on an angle to clear the lug 35. With the pistol gripsection 40 of the handle member removed, the lower brush 22 may bereplaced through the recess or notch 39 provided in the lower edge ofthe motor case for the lug 38 on the grip section 40. The large spaceprovided above the cup ll enables the commutator to be readily andeasily reached for cleaning, as by the use of a piece of sand paper asused for large stationary motors.

The particular tool shown has a universal motor, for either A. C. or D.C. current and has a free speed of approximately 2500 revolutions perminute.

The electrical circuit of the tool is as follows: The cable wire I6 isconnected to one of the field coil leads 10. The other field coil leadII is connected to the binding screw 30 of the lower brush holder. Thecable wire I! is connected to one of the switch wires 12. The otherswitch wire 13 is connected to the post 33 of the upper brush holder.

The handle member 32 on being released from the motor case I to view thebrush assembly, etc. is dropped down the cable It. On assembling thetool in the first instance, the cable I5 is inserted into the handlemember 32 through the opening 43 in the closure disc, whereupon thecable is clamped to the bracket I3 and the connections made with themotor. On completion of the motor switch and gear assembly, the handleis secured in place over the rear end of the motor case. On assemblingthe motor, the

stator 4 is inserted into the casing I through the open front endthereof, and is fastened in place by a number of set screws carried bythe case I, one screw being shown at N in Fig. 1. All of the wiring forthe motor circuit has tight connections which avoid faulty electricalcontacts. It will be noted that the switch device 6 is not screwed inplace, the clamping arrangement shown enabling a single snap switch tobe used and mounted.

The details of construction and arrangement of parts shown and describedmay be variously changed and modified without departing from the spiritand scope of my invention, except as pointed out in the annexed claims.

I claim as my invention:

1. In a portable electric tool of the character described, a motor case,an electric motor in said case, a spindle at the forward end of the caseand driven by said motor, a brush assembly and a supply cable for themotor at the rear end of said case, and a handle member releasablysecured to the rear end of the motor case over the brush assembly andthe supply cable and providing a closure therefor, said handle memberhaving a pistol grip portion extending below the motor case, said brushassembly and the supply cable being supported wholly by the motor case,whereby the handle member including the whole of its pistol grip portionmay be removed from the motor case without disturbing the brush assemblyor. the supply cable.

2. In a portable electric tool of the" character described, a motorcase, an electric motor in said case, a spindle at the forward end ofthe case and driven by the motor, a bearing cup and a brush' assemblyfor the motor at the rear end of said case, a supply cable for the motorsecured to said cup, and a handle member releasably secured to the rearendof the motor case over the bearing cup and the supply cable andproviding a closure therefor, said handle member having a pistol gripportion extending below the motor case, said brush assembly and bearingcup being wholly supported by the motor case, whereby the handle memberincluding the whole of its pistol grip portion maybe in one piece and beremovable as a unit from the motor case without disturbing the brushassembly or the supply cable.

3. In a portable electric tool of the character described, a motor case,an electric motor in said case, a spindle at the forward end of the caseand driven by said motor, a brush assembly and a supply cable for themotor at the rearend of the motor case, a handle member releasablysecured to the rear end of the motor case over the brush assembly andthe supply cable and providing a closure therefore, said handle memberhaving a pistol grip portion extending below the motor case, said brushassembly and the supply cable being wholly supported by the motorcasing, whereby the handle member including its pistol grip portion maybe removed from the motor case without disturbing the brush assembly orthe supply cable, and interfitting means on the handle member and themotor case to interlock the handle member to'the motor case when thehandle member is secured to the motor case.

4. In a portable electric tool of the character described, a motor case,an electric motor in said case, a spindle at the forward end of the caseand driven by the motor, a brush assembly having upper and lower brushesand a supply cable for the motor at the rear end of the motor case, ahandle member releasably secured to the rear end of the motor case overthe brush assembly and the supply cable and providing a closuretherefor, said handle member having a pistol grip portion extendingbelow the motor case, said brush assembly and the supply cable beingsupported wholly by the motor case, whereby the 'handle member includingits pistol grip portion may be removed from the motor case withoutdisturbing the brush assembly or the supply cable, said motor casehaving a space above the motor for the removal of the upper brush and arecess in the lower rear edge of the motor case below the motor for theremoval of the lower brush.

5. In a portable electric tool of the character described, a motor case,an electric motor in said case, a spindle at the forward end of the caseand driven by the motor, said case'having a pair of rearwardlyprojecting, laterally spaced lugs at its rear end, a bearing for therear end of the motor, a cup for the bearing between and supported bysaid lugs, a bracket depending from said cup, a supply cable for themotor clamped to said bracket, and a handle member releasably secured tothe rear end of the motor case over said cup and said bracket andproviding a closure therefor, said handle member having a pistol gripportion extending below the motor case,-said handle member havingrceesses to receive and interfit the lugs on the motor case when thehandle member is secured thereto.

6. In a portable electric tool of the character described, a motor case,an electric motor in said case and having its commutator adjacent therear end of the case, a spindle at the forward end of the case anddriven by the motor, a brush assembly forthe commutator and a supplycable for the motor, both located at the rear end of the motor case, anda handle member at the rear end of the motor case having a pistol gripportion extending below the case, said brush assembly and the supplycable being wholly supported by the motor case, said handle memberproviding a closure for the rear and of the motor case and beingreleasably secured thereto, whereby an unobstructed view and access maybe had to the brush assembly and the commutator on removing the handlemember including its pistol grip portion from the motor case.

7. In a portable electric tool of the character described, a motor case,an electric motor in said case, a spindle at the forward end of the caseand driven by the motor, a handle member secured to the rear end of thecase and having a pistol grip portion extending below the case, saidmotor being disposed in the lower portion of the case to provide a spacebetween the motor and the top wall of the motor case, a switch devicefor the motor, said switch device being located in said space adjacentthe spindle, and means disposed in said space and connected with theswitch device for actuating the same, said means extending along thespace toward the handle member and operable from the exterior of themotor case adjacent the handle member.

8. In a portable electric tool of the character described, a motor case,an electric motor in said case, a spindle at the forward end of the caseand driven by the motor, a handle member secured to the rear end of thecase and having a pistol grip portion extending below the case, saidmotor being disposed in the lower portion of the case to provide a spacebetween the motor and the top wall of the motor case, a switch devicefor the motor, said switch device being 10- cated in said space adjacentthe spindle, a lever pivoted in the space adjacent the handle member andoperable from the exterior of the case adjacent the handle member, asecond lever pivoted in the space between the switch device and thefirst lever, said second lever extending along the space from the switchdevice to the first lever and having one end at the first lever and itsother end engaged with the switch device for operating the same, and acam connection between the first and the second levers for actuating thesecond lever by the first lever.

9. In a portable electric tool of the character described, a motor case,an electric motor in said case, a spindle at the forward end of saidcase and driven by the motor, a handle member secured to the rear end ofthe case and having a. pistol grip portion extending below the case,said motor being disposed in the lower portion of the case to provide aspace between the motor and the top wall of the motor case, a switchdevice for the motor, said switch device being located in said spaceadjacent the spindle, a lever pivoted in the space adjacent the handlemember and operable from the exterior of the case adjacent the handlemember, and a second lever pivoted in the space between the switchdevice and the first lever, said second lever extending along the spacefrom the switch device to the first lever and having one end at thefirst lever and its other end engaged with the switch device foroperating the same, said first lever being disposed substantially normalto the second lever and having a cam slot cooperable with the secondlever for operating the same.

10. In a portable electric tool of the character described, a motorcase, an electric motor in said case, a spindle at the forward end ofthe case and driven by the motor, a cover plate closing the front end ofthe case, a handle member closing the rear end of the case and having apistol grip portion extending below the case, said motor being disposedin the lower portion of the case to provide a space between the motorand the top of the case, a switch device for the motor, said switchdevice being located in said space adjacent the cover plate andsupported thereby, means for holding the switch device in place withrespect to the cover plate, and means in said space and connected withthe switch device for operating the same, said means extending along thespace toward the handle member and being operable from the exterior ofthe motor case adjacent the handle member.

11. In a portable electric tool of the character described, a motorcase, an electric motor in said case, a spindle at the forward end ofthe case and driven by the motor, brushes for the motor at the rear endof the case, a handle member releasably secured to the rear end of themotor case over the brushes and providing a closure therefor, saidhandle member having a pistol grip portion extending beyond the motorcase, said brushes being supported by the motor case, whereby the handlemember including the whole of its pistol grip portion may be removedfrom the motor case without disturbing the brushes with respect to themotor, and a supply cable associated withthe handle member for themotor.

12. In a portable electric tool of the character described, a motorcase, an electric motor in said case, a spindle at the forward end ofthe case and driven by the motor, brushes at the rear end of the motorcase, a handle member releasably secured to the rear end of the motorcase over the brushes and providing a closure therefor;

said handle member having a grip portion extending outwardly from themotor case, said brushes being supported by the motor case, whereby thehandle member including the whole of its grip portion may be removedfrom the motor case without disturbing the brushes with respect to themotor, and a cooling system for the motor comprising a fan member at thefront end of the motor and driven thereby, and air intake and dischargeopenings in the motor case, the intake openings being adjacent to and inadvance of the brushes and the discharge openings being adjacent to theperiphery oi the fan.

13. In a portable electric tool of the character described, a motorcase, an electric motor in said case, a spindle at the forward end ofthe case and driven by the motor, brushes for the motor at the rear endof the motor case, a. handle member releasably secured to the rear endof the motor.

FRI'I'HIOP P. FORSS.

